How to know if a field is numeric in Linq To SQL

Question

I need to select the rows of a table where a column value is numeric, any Help?

EDIT: I have a varchar column and I need to select the ones that are numbers and the

Answer 1

Look into Int32.TryParse ... That may work for you.

Ian

Answer 2

(Edited to suit your needs)

So, given the fact that you cannot use Integer.TryParse, the following is not feasible:

int i;
var rowsWithInts = (From r In dc.YourRows Where Integer.TryParse(r.Column, i));
var rowsWithoutInts = (From r In dc.YourRows Where !Integer.TryParse(r.Column, i));

Is it possible that you create a stored procedure and link it to the DataContext via the Methods Pane? In that case you can do in your SQL the following:

-- Rows with integers
SELECT * FROM your_table WHERE ISNUMERIC(varchar_column) = 1
-- Rows without integers
SELECT * FROM your_table WHERE ISNUMERIC(varchar_column) = 0

Does this helps?

Answer 3

I don't know if there is a mapping for int.TryParse() in LinqToSQL, but you could probably do it in two steps by performing the query, casting to a List, then selecting out of the list with LinqToObjects.

int i;
var query = context.Table.ToList();
var intQuery = query.Where( t => int.TryParse( t.Column, out i ) );

You might want to look at Dynamic LINQ, too. That would allow you to do something like:

var query = context.Table.Where( "IsNumeric(Column)" );

EDIT Dynamic LINQ is available in the VS2008 Code Samples, linked to from Scott Guthrie's blog, which I've linked above.

Answer 4

<>.Where(x=>"0123456789".IndexOf(x.value.substring(0,1))>-1)

Answer 5

You will not be able to do this with LINQ2SQL without loading all records on the client.

I can suggest to create view or table-valued function with aditional calculated column and then filter your results with this column. Or execute regular SQL with DataContext.ExecuteQuery.

Answer 6

Open up your DBML (LINQ-to-SQL) file in an XML editor, go down to the end of the file and paste this just before the '</Database>' node:

<Function Name="ISNUMERIC" IsComposable="true">
    <Parameter Name="Expression" Parameter="Expression" Type="System.String" DbType="NVarChar(4000)" />
    <Return Type="System.Boolean" DbType="BIT NOT NULL"/>
</Function>

Now, you can use the already-in-SQL function called "ISNUMERIC". Here's how:

var blah = myDataContext.Accounts.Where(account=>
    myDataContext.ISNUMERIC(account.ID) == true);

There you go :)

You may also find these functions useful to copy:

<Function Name="RAND" IsComposable="true">
  <Return Type="System.Double" DbType="Float NOT NULL" />
</Function>
<Function Name="NEWID" IsComposable="true">
  <Return Type="System.Guid" DbType="UniqueIdentifier NOT NULL" />
</Function>